U.S. patent application number 14/450115 was filed with the patent office on 2015-02-12 for image heating apparatus.
The applicant listed for this patent is CANON KABUSHIKI KAISHA. Invention is credited to Shigeru Hirano, Ikuo Nakamoto.
Application Number | 20150043953 14/450115 |
Document ID | / |
Family ID | 52448775 |
Filed Date | 2015-02-12 |
United States Patent
Application |
20150043953 |
Kind Code |
A1 |
Nakamoto; Ikuo ; et
al. |
February 12, 2015 |
IMAGE HEATING APPARATUS
Abstract
A fixing apparatus includes a fixing belt, a pressure roller, a
heater, a stay holder, and a scraper. The fixing belt is configured
to heat an image on a sheet at a nip portion and has an inner
surface with a grease applied thereon. The pressure roller drives
and rotates the fixing belt and forms the nip portion between the
pressure roller and the fixing belt. The heater and the stay holder
press the fixing belt toward the pressure roller from the inner
surface of the fixing belt. The scraper scrapes the lubricant
transferred to the pressure roller in an area that can come into
contact with the fixing belt and that does not come into contact
with a maximum width sheet introducible into the fixing apparatus
on one end side in a rotational axis direction of the pressure
roller.
Inventors: |
Nakamoto; Ikuo;
(Matsudo-shi, JP) ; Hirano; Shigeru; (Toride-shi,
JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
CANON KABUSHIKI KAISHA |
Tokyo |
|
JP |
|
|
Family ID: |
52448775 |
Appl. No.: |
14/450115 |
Filed: |
August 1, 2014 |
Current U.S.
Class: |
399/329 |
Current CPC
Class: |
G03G 15/2025 20130101;
G03G 15/2053 20130101 |
Class at
Publication: |
399/329 |
International
Class: |
G03G 15/20 20060101
G03G015/20 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 9, 2013 |
JP |
2013-166255 |
Claims
1. An image heating apparatus comprising: an endless belt
configured to heat an image on a sheet at a nip portion, the
endless belt having an inner surface on which a lubricant is
applied; a driving rotator configured to drive and rotate the
endless belt and form the nip portion between the driving rotator
and the endless belt; a pressing member configured to press the
endless belt toward the driving rotator from the inner surface of
the endless belt; and a scraping member configured to scrape the
lubricant transferred from the endless belt to the driving rotator,
the scraping member scraping the lubricant on the driving rotator
in an area that can come into contact with the endless belt and
that does not come into contact with a maximum width sheet
introducible into the image heating apparatus on one end side in a
rotational axis direction of the driving rotator.
2. The image heating apparatus according to claim 1, further
comprising: another scraping member configured to scrape the
lubricant transferred from the endless belt to the driving rotator,
wherein the another scraping member scrapes the lubricant on the
driving rotator in an area that can come into contact with the
endless belt and that does not come into contact with the maximum
width sheet introducible into the image heating apparatus on
another end side in the rotational axis direction of the driving
rotator.
3. The image heating apparatus according to claim 2, wherein the
scraping members comprise unwoven fabric.
4. The image heating apparatus according to claim 1, wherein the
pressing member includes a heating member configured to heat the
endless belt.
5. The image heating apparatus according to claim 1, wherein the
driving rotator is a roller.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to an image heating apparatus
for heating a toner image on a sheet. The image heating apparatus
can be used in, for example, an image forming apparatus of the
electrophotographic type or electrostatic recording type, such as a
printer, a copier, a facsimile machine, and a multifunction machine
having a plurality of functions of them.
[0003] 2. Description of the Related Art
[0004] Nowadays, image forming apparatuses need quick response
(time from transmission of a print instruction to outputting of an
image; hereinafter referred to as wait time). A reduction in the
wait time is greatly affected by the warm-up time of a fixing
apparatus (image heating apparatus).
[0005] A fixing apparatus that uses a thin endless belt having a
low heat capacity (hereinafter referred to as belt) is described in
Japanese Patent Laid-Open No. 8-305187. Specifically, the fixing
apparatus employs the technique of pressing the belt using a
ceramic heater from its inside toward a pressure roller and driving
and rotating the belt using the pressure roller. The use of that
technique aims to reduce the wait time.
[0006] In the fixing apparatus employing that technique, because
the belt slides on the ceramic heater, a heat-resistant lubricant,
such as grease or oil, is applied on the inner surface of the belt.
The heat-resistant lubricant reduces the frictional resistance
between the inner surface of the belt and the ceramic heater, thus
facilitating the rotation of the belt driven by the pressure
roller.
[0007] The fixing apparatus described in Japanese Patent Laid-Open
No. 8-305187 includes blades for removing the lubricant. The blades
are disposed on the outer surface of the belt on both ends in the
width direction. The blades are included to prevent the lubricant
leaking out from the ends of the belt with prolonged use of the
fixing apparatus from moving to the outer surface of the belt and
adhering to a sheet.
[0008] However, because the blades for removing the lubricant in
the fixing apparatus described in Japanese Patent Laid-Open No.
8-305187 are in contact with the belt, stability of rotation of the
belt may be degraded. The conceivable reason for this is that
friction caused by the state where the blades are in contact with
the belt acts as a force inhibiting the driven rotation of the
belt. If the stability of rotation (running) of the belt is
inhibited, supplying heat to a sheet becomes instable, and this may
lead to an image defect, such as a fixing failure or gloss
unevenness.
SUMMARY OF THE INVENTION
[0009] The present invention provides an image heating apparatus
capable of discouraging adhesion of a lubricant to a sheet.
[0010] Further features of the present invention will become
apparent from the following description of exemplary embodiments
with reference to the attached drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] FIG. 1 is an explanatory view of a configuration of an image
forming apparatus according to a first embodiment.
[0012] FIG. 2 is an explanatory view of a configuration of a fixing
apparatus according to the first embodiment.
[0013] FIG. 3 is a cross-sectional explanatory view of the fixing
apparatus taken along the line III-III in FIG. 2.
[0014] FIG. 4 is an exploded explanatory view of the fixing
apparatus.
[0015] FIG. 5 is an explanatory view of an example configuration of
a heater (ceramic heater).
[0016] FIG. 6 is a cross-sectional explanatory view of a flange
portion and a fixing belt.
[0017] FIG. 7 is a perspective explanatory view of a rotational
flange.
[0018] FIG. 8 is a cross-sectional explanatory view of a fixing
apparatus according to a second embodiment taken along the line
VIII-VIII in FIG. 2.
DESCRIPTION OF THE EMBODIMENTS
[0019] Embodiments of the present invention are described in detail
below with reference to the drawings. In the following embodiments,
an image heating apparatus according to the present invention is
described as a fixing apparatus for fixing an unfixed toner image
on a printing medium (sheet). The image heating apparatus can also
be implemented as a heating processor for heating and pressing a
printing medium that bears a fixed image or a semi-fixed image to
adjust the state of the surface of the image.
First Embodiment
[0020] First, an image forming apparatus is described with
reference to FIG. 1. FIG. 1 is an explanatory view for describing a
configuration of the image forming apparatus that incorporates a
fixing apparatus functioning as an image heating apparatus. The
image forming apparatus illustrated in FIG. 1 is a laser-beam
printer that employs a transfer-type electrophotographic
process.
[Image Forming Apparatus]
[0021] As illustrated in FIG. 1, the image forming apparatus
includes a photosensitive drum 1, a charging roller 2, a laser
scanner 3, a developing device 4, and a transfer roller 5. The
charging roller 2, laser scanner 3, developing device 4, and
transfer roller 5 are disposed around the photosensitive drum 1
along its rotational direction. A toner image T is formed through
processes for forming a latent image, developing the image, and
transferring the image.
[0022] The photosensitive drum 1 in the present embodiment is one
example of an electrophotographic photosensitive member as an
image-bearing member. The photosensitive drum 1 includes a
cylindrical conductive substrate made of aluminum, nickel, or other
material and a photosensitive layer on the substrate. The
photosensitive layer can be made of a photosensitive material, such
as organic photoconductor (OPC), amorphous selenium, or amorphous
silicon.
[0023] The photosensitive drum 1 rotates at a predetermined
circumferential speed in the clockwise direction indicted by the
arrow in FIG. 1. First, the surface of the photosensitive drum 1 is
charged uniformly to a predetermined polarity and potential by the
charging roller 2 as a charger.
[0024] Then, the uniformly charged surface is subjected to a
scanning exposure 3a, and an electrostatic latent image is formed
thereon. The scanning exposure 3a is performed by the laser scanner
3 controlling an ON/OFF state of a laser beam in accordance with an
image signal.
[0025] The electrostatic latent image is developed and visualized
as the image T by the developing device 4 containing black toner.
Examples of a developing method may include a jumping development
method, a two-component developing method, and a FEED development
method. The combination of image exposure and reverse development
is typically used.
[0026] The visualized image T is conveyed to the transfer roller 5
by rotation of the photosensitive drum 1. The conveyed image T is
transferred from the photosensitive drum 1 to a sheet P by the
transfer roller 5 as a transfer device.
[0027] At this time, a sensor 8 detects the leading edge of the
conveyed sheet P, and this is used in controlling timing for
conveying the sheet P. The sheet P is conveyed such that its
writing position and the image formation position of the image T on
the photosensitive drum 1 match with each other in the position of
the transfer roller 5.
[0028] The conveyed sheet P is nipped and conveyed between the
photosensitive drum 1 and the transfer roller 5. The image T on the
photosensitive drum 1 is sequentially transferred to the sheet
P.
[0029] The sheet P with the transferred image T is separated from
the photosensitive drum 1 and introduced into a fixing apparatus 6.
The fixing apparatus 6 corresponding to the image heating apparatus
fixes the toner image on the sheet by applying heat and pressure
thereon.
[0030] The sheet P with the fixed toner image is discharged out of
the image forming apparatus.
[0031] When the sheet P is separated from the photosensitive drum
1, toner that has not been transferred to the sheet P remains on
the surface of the photosensitive drum 1. A cleaning device 7
cleans the photosensitive drum 1 by removing the remaining toner
and enables images to be formed repeatedly.
[Fixing Apparatus]
[0032] Next, a configuration of the fixing apparatus 6 is described
in detail with reference to the drawings. FIG. 2 is an explanatory
view of the configuration of the fixing apparatus according to the
present embodiment. FIG. 3 is a cross-sectional explanatory view of
the fixing apparatus 6 taken along the line III-III in FIG. 2. FIG.
4 is an exploded explanatory view of the fixing apparatus. In the
following description, the width direction of the fixing apparatus
6 or members included therein is a direction substantially parallel
with a direction perpendicular to a sheet conveying direction in a
sheet conveying path plane and is a direction substantially
parallel with a rotational axis direction of the pressure roller.
In the description about the fixing apparatus 6, the frontal
surface is a surface viewed from the side which a sheet enters, and
the rear surface is a surface opposite the frontal surface (surface
on the sheet outlet side). Left and right are left (near side) and
right (far side), respectively, viewed from the frontal surface of
the apparatus. The upstream and downstream sides are the ones in
the sheet conveying direction.
[0033] As illustrated in FIG. 3, the fixing apparatus 6 according
to the present embodiment is an apparatus of the belt (film)
heating type and the pressing member driving type using a
cylindrical metallic belt (endless belt that heats the image T on a
sheet at a nip portion N) as a heating member. The fixing apparatus
6 serves the function of heating an unfixed image T borne on the
sheet P passing through the nip portion N using a fixing belt
10.
[0034] As illustrated in FIG. 2, the fixing apparatus 6 includes a
heating unit 9, a pressure roller 20, and an apparatus housing
(sheet-metal frame) 30 including right and left side plates 31. The
heating unit 9 and the pressure roller 20 are held substantially in
parallel with each other by the right and left side plates 31. The
heating unit 9 and the pressure roller 20 are in pressure contact
with each other and thus constitute the nip portion N.
[0035] The heating unit 9 has the function of heating the image T
on the sheet passing through the nip portion N. The heating unit 9
is urged toward the pressure roller 20 such that the heating unit 9
constitutes the nip portion N in cooperation with the pressure
roller 20.
[0036] As illustrated in FIG. 3, the heating unit 9 is an assembly
of a plurality of components described below.
[0037] A stay holder 12 having heat resistance and rigidity and
extending in the width direction.
[0038] A heater 11 corresponding to a heating member, fit in a
recess 12a (see FIG. 3) in the surface opposite to the fixing belt
10 of the stay holder 12, fixed and supported therein, and
generating heat by energization.
[0039] The fixing belt 10 corresponding to an endless belt, fit on
the outside of the stay holder 12 so as to cover the stay holder
12, and having the inner surface with grease applied thereon.
[0040] A flange portion 15 attached on each of both ends of the
stay holder 12 in the width direction and functioning as a
regulator configured to regulate lateral movement toward the width
direction (direction of the generatrix) of the fixing belt 10.
[0041] Accordingly, the fixing apparatus 6 includes the components
described below.
[0042] The fixing belt 10 corresponding to an endless belt and
configured to heat the image T on the sheet P at the nip portion
N.
[0043] The pressure roller 20 corresponding to a driving rotator
and forming the nip portion N between the pressure roller 20 and
the fixing belt 10.
[0044] The heater 11 and the stay holder 12 corresponding to a
pressing member and configured to press the fixing belt 10 from its
inner surface side toward the pressure roller 20.
[0045] The fixing apparatus 6 further includes scrapers 60
configured to a scraping member configured to remove a lubricant,
in addition to the above components. The details of the scrapers 60
are described below.
[0046] As illustrated in FIG. 3, the pressure roller 20
corresponding to the driving rotator is rotated in the
counterclockwise direction indicated by the arrow in the drawing.
The pressure roller 20 constitutes the nip portion N in cooperation
with the heating unit 9, and thus conveys the sheet P nipped by the
nip portion N in a leftward direction indicated by the arrow in the
drawing.
[0047] The pressure roller 20 includes a cylindrical core bar 21,
an elastic layer 22 covering the core bar 21, and a release layer
23 for facilitating release of toner. The release layer 23 coats
the elastic layer 22 with a heat-resistant resin material. As the
release layer 23 in the present embodiment, tetrafluoroetylene
perfluoroalkylvinylether copolymer (PFA) is used.
[0048] As illustrated in FIG. 4, each of the right and left side
plates 31 in the apparatus housing 30 has an opening in its upper
side. Each of the right and left side plates 31 has a fit slit 31a
having a shape in which the opening extends toward the inside of
the side plate 31. The width of the opening is Lb. The fit slits
31a in the right and left side plates 31 have the same shape (are
symmetrical).
[0049] A bearing member 32 is arranged on the bottom of each of the
fit slits 31a. The bearing member 32 includes a fitting section 32a
and engages with the apparatus side plate 31. The right and left
bearing members 32 hold the pressure roller 20 between the left and
right side plates 31 by supporting the right and left ends of the
core bar 21 so as to allow the pressure roller 20 to be freely
rotatable.
[0050] Each of the right and left flange portions 15 includes a
fitting section 15c fit in the fit slit 31a. Thus the heating unit
9 is arranged above the pressure roller 20 and between the left and
right side plates 31.
[0051] Each of the right and left flange portions 15 includes a
pressing section 15d. The pressing section 15d is pressed by a
pressing spring 17 (described below). Thus the heating unit 9 is
urged toward the pressure roller 20.
[0052] The shrinkable pressing spring 17 (elastic member) is
arranged between the pressing section 15d and a spring receiving
member 40 fixed on the apparatus housing 30. The pressing section
15d is pressed by the elastic force of the pressing spring 17. The
heating unit 9 urged toward the pressure roller 20 presses the
fixing belt 10 against the upper surface of the pressure roller 20
by a predetermined pressing force (elastic force). The fixing belt
10 and the pressure roller 20 constitute the nip portion N having a
predetermined width by being pressed against their respective
elasticity.
[0053] The heating unit 9 is urged toward the pressure roller 20
through the stay holder 12 and the heater 11. Accordingly, in the
present embodiment, the heater 11 and the stay holder 12 function
as a pressing member. As illustrated in FIG. 3, at the nip portion
N, the fixing belt 10 is sandwiched between the lower surface of
the stay holder 12 holding the heater 11 and the upper surface of
the pressure roller 20. The fixing belt 10 is warped along the
shape of the lower surface of the stay holder 12, and its inner
surface is in close contact with the flat surface of the lower
surface of the stay holder 12 and the lower surface of the heater
11.
[0054] A driving gear G is fixed on one end side of the core bar 21
in the pressure roller 20. The driving gear G receives a rotational
force from a motor (driving portion) M, and thus the pressure
roller 20 is rotated at a predetermined rotational speed in the
counterclockwise direction indicated by the arrow in FIG. 3. With
the rotation of the pressure roller 20, a friction occurs between
the pressure roller 20 and the fixing belt 10 in the heating unit 9
at the nip portion N. This friction causes the fixing belt 10 to
receive a force for rotating the fixing belt 10. Accordingly, the
fixing belt 10 is in a state where it rotates in the clockwise
direction indicated by the arrow in FIG. 3 around the stay holder
12 while sliding such that the inner surface of the fixing belt 10
is in close contact with the lower surface of the heater 11
(pressure roller driving type).
[0055] The fixing belt 10 frictionally slides on the heater 11 and
the stay holder 12 disposed inside by its rotation driven by the
pressure roller 20. To suppress abrasion of the fixing belt 10
caused by that frictional sliding and stabilize the driven
rotation, the frictional resistance between the fixing belt 10 and
each of the heater 11 and the stay holder 12 can be reduced. To
this end, in the present embodiment, a lubricant, such as a
heat-resistant grease, is applied on the surface of each of the
heater 11 and the stay holder 12 and the inner peripheral surface
of the fixing belt 10. This enables smooth rotation of the fixing
belt 10.
[0056] The heater 11 as the heating member heats the nip portion N
to melt and fix the image T on the sheet P through the fixing belt
10. The following specific description is based on a state where
rotation of the pressure roller 20 causes rotation of the fixing
belt 10, the heater 11 is energized, the temperature of the heater
11 rises to a predetermined temperature, and the temperature is
adjusted.
[0057] First, the sheet P bearing an unfixed image T is conveyed
between the fixing belt 10 and the pressure roller 20 at the nip
portion N along a fixing inlet guide 24. Then, the sheet P is
conveyed while being nipped at the nip portion N, and the unfixed
image T is heated and fixed by heat from the heater 11 through the
fixing belt 10. After that, the sheet P having passed through the
nip portion N becomes separated from the outer surface of the
fixing belt 10, is guided by a fixation discharging guide (not
illustrated), and is discharged onto a discharge tray (not
illustrated).
[0058] The fixing belt 10 as the endless belt is a flexible sleeve
having a small thermal capacity. More specifically, the fixing belt
10 includes a base layer made of a high thermal conductive metal
material having high heat resistance and has a total thickness of
500 .mu.m or less to enable a fixing process to quickly start. As
the metal material, a metal, such as aluminum, nickel, copper, or
zinc, or an alloy selecting from these metals may be used. To have
an increased life of the fixing apparatus, the fixing belt 10 may
preferably have a total thickness of 30 .mu.m or more as a metal
sleeve having a sufficient strength and a good durability.
Accordingly, the total thickness of the fixing belt 10 may
preferably be in the range of 30 .mu.m to 500 .mu.m.
[0059] The surface layer of the fixing belt 10 is coated with PFA
as a heat-resistant resin having good releasability to prevent
offset and ensure separability of the sheet P. As the
heat-resistant resin having good releasability, a mixture or a
single component selected from fluoroplastics and silicone resins
described below may be used. Examples thereof may include
polytetrafluoroethylene (PTFE), fluorinated-ethylene-propylene
copolymer (FEP), ethylene tetrafluoro ethylene copolymer (ETFE),
polychlorotrifluoroethylene (CTFE), and polyvinylidene fluoride
(PVDF).
[0060] The inner surface of the metal sleeve in contact with the
heater 11 may be overlaid with a layer having enhanced lubricity,
such as a fluoroplastic layer, a polyimide layer, or a polyamide
imide layer. In the present embodiment, the application of grease
on the inner surface of the belt 10 facilitates sliding with the
heater 11.
[0061] FIG. 5 is an explanatory view of an example configuration of
the heater 11.
[0062] The heater 11 is a member for heating the fixing belt 10 to
melt and fix the image T on the sheet P at the nip portion N.
[0063] As illustrated in FIG. 5, the heater 11 includes components
described below.
[0064] A ceramic substrate (heater substrate) 11a made of a highly
insulating ceramic and having a horizontally long shape.
[0065] A resistive layer 11b formed along the longitudinal
direction (width direction) on the front side of the ceramic
substrate 11a.
[0066] Electrode portions 11c made of silver/platinum (Ag/Pt) and
formed by providing conduction of electricity to the both ends of
the resistive layer 11b in the longitudinal direction.
[0067] An insulating protective layer 11d, such as a glass coating
or fluoroplastic coating, being thin, capable of enduring
frictional sliding with the metal fixing belt 10, disposed on the
front side of the resistive layer 11b, and electrically
insulating.
[0068] A temperature sensing element 14, such as a thermistor,
disposed on the back (rear surface) side of the ceramic substrate
11a.
[0069] A highly insulating ceramic, such as the one made of
aluminum nitride (AlN), or a heat-resistant resin, such as
polyimide, polyphenylene sulfide (PPS), or a liquid polymer, can be
used in the ceramic substrate 11a. The resistive layer 11b is
formed by applying a material, such as silver/palladium (Ag/Pd),
uthenium oxide (RuO.sub.2), or tantalum nitride (Ta.sub.2N), on the
substrate by, for example, screen printing. The resistive layer 11b
has a linear or strip shape with a thickness of the order of
approximately 10 .mu.m and a width of the order of 1 to 5 mm.
[0070] In the above-described heater 11, the side on which the
insulating protective layer 11d is disposed is the front side, and
the fixing belt 10 slides on the surface of the insulating
protective layer 11d. The heater 11 is fit in the recess 12a (see
FIG. 3), which extends along the longitudinal direction of the stay
holder 12 in the lower surface of the stay holder 12, bonded with a
heat-resistant adhesive, and held therein.
[0071] Electric supply connectors 51 are attached to the electrode
portions 11c in the heater 11 fixed and supported by the stay
holder 12 and include electric contacts being in contact with the
electrode portions 11c. A commercial power source (AC) 52, a triac
53, and an electric power (energization) controller (CPU) 54 are
connected (AC line). The temperature of the heater 11 quickly is
raised by heat of the resistive layer 11b generate by electric
power supplied between the electrode portions 11c from the
commercial power source 52 through the triac 53.
[0072] The rise of temperature in the heater 11 is sensed by the
temperature sensing element 14 being a temperature sensing member.
Electric analog information on the sensed temperature is input into
an analog-to-digital converting circuit (A/D converting circuit) 55
and is digitized. The digital information is input into the
electric power controller 54. DC energization is performed from the
temperature sensing element 14 to a temperature control portion by
a connector (not illustrated) through a DC energization portion and
DC electrode portion (not illustrated).
[0073] In accordance with a signal from the temperature sensing
element 14, a duty ratio of a voltage applied from the electrode
portions 11c on the ends of the heater 11 in the longitudinal
direction to the resistive layer 11b, the number of waves, and
other factors are properly controlled. The adjusted temperature in
the nip portion N is maintained substantially constant, and heating
sufficient for fixing the image T on the sheet P is carried out.
That is, the electric power controller 54, which receives digital
information corresponding to the temperature sensed by the
temperature sensing element 14, is configured to control
energization from the commercial power source 52 to the resistive
layer 11b such that the temperature sensed by the temperature
sensing element 14 is a value in a range having a predetermined
width from a target temperature.
[0074] Examples of a method of controlling energization from the
commercial power source 52 to the resistive layer 11b by the
electric power controller 54 are described below. One example is
phase control of changing a phase range for the energization from
the commercial power source 52 to the resistive layer 11b for each
half-wave period of the AC power supply output from the commercial
power source 52 in accordance with the temperature sensed by the
temperature sensing element 14. Another example is wave number
control of switching between energization from the commercial power
source 52 to the resistive layer 11b and non-energization for each
half-wave period of the AC power supply output from the commercial
power source 52 in accordance with the temperature sensed by the
temperature sensing element 14.
[0075] When a highly thermally conductive material having high wear
resistance, such as aluminum nitride, is used in the ceramic
substrate 11a, the resistive layer 11b may be disposed on the side
of the ceramic substrate 11a opposite to the nip portion N.
[0076] The stay holder 12 performs the function of supporting the
heater 11 and serves as a member for guiding rotation of the fixing
belt 10, as a pressing member, and as a thermal insulating member
to prevent heat dissipation in a direction opposite to the nip
portion N. Accordingly, the stay holder 12 functions as both the
pressing member and first and second guide portions. The stay
holder 12 is a rigid, heat-resistant, adiabatic member made of, for
example, a liquid polymer, phenol resin, PPS, or
polyetheretherketone (PEEK).
[0077] In the present embodiment, a section downstream of the nip
portion N in the stay holder 12 projects toward the pressure roller
20 as a projecting section K having a height of 1.0 mm (see FIG. 3;
jaw section for changing the curvature of the fixing belt 10). The
projecting section K is used for changing the rotational shape of
the fixing belt 10 and separating the sheet P from the fixing belt
10 using the changed curvature.
[0078] FIG. 6 is a cross-sectional explanatory view of the flange
portion and the fixing belt. FIG. 7 is a perspective explanatory
view of a rotational flange.
[0079] The flange portion 15 is arranged on each of both right and
left ends (first and second ends) of the stay holder 12 functioning
as the first and second guide portions. The flange portion 15
regulates lateral movement of the fixing belt 10 in the width
direction on each of both ends of the pressure roller 20. As
illustrated in FIG. 6, the flange portion 15 includes a rotational
flange 15A and a fixed flange 15B. The rotational flange 15A is a
member having a ring shape with no end or a disc shape. The
rotational flange 15A performs driven rotation by abutting the end
face of the rotating fixing belt 10. The fixed flange 15B is a
member whose rotation is regulated by the side plate 31. The fixed
flange 15B regulates movement of the rotational flange 15A in the
width direction caused by the fixing belt 10.
[0080] The fixed flange 15B is made of a heat-resistant resin, such
as PPS, a liquid polymer, or phenol resin. The fixed flange 15B has
a cap shape and includes an insertion section 15a in its inner
surface side. The insertion section 15a has an inside diameter
allowing the rotational flange 15A as a first regulating member to
be inserted therein. The inside diameter has a sufficiently large
size in which even if the outer peripheral shape of the fixing belt
10 is deformed by forming the nip, the outer peripheral surface of
the fixing belt 10 does not come into contact with the inner
peripheral surface of the insertion section 15a. The fixed flange
15B as a member for regulating the rotational flange 15A regulates
the rotational flange 15A in the width direction and regulates the
position of rotation of the rotational flange 15A.
[0081] The rotational flange 15A is made of PPS, which is a
heat-resistant resin. Another heat-resistant resins, such as a
liquid polymer or phenol resin, may also be used. The rotational
flange 15A has a ring cap shape, as illustrated in FIG. 7. The
rotational flange 15A has an outside diameter Lo smaller than the
inside diameter of the insertion section 15a in the fixed flange
15B and larger than a cut section 15b. The rotational flange 15A
has an inside diameter Li having a size that does not interfere
with the heater 11. An outward extended portion 12b in the stay
holder 12 is positioned within the inside diameter Li. The
rotational flange 15A is arranged so as not to interfere with the
outward extended portion 12b in the stay holder 12. The rotational
flange 15A prevents frictional sliding of the end face of the
fixing belt 10 by rotating together with the fixing belt 10 while
its inside is in contact with the fixing belt 10.
[Scraper]
[0082] In the fixing apparatus 6 according to the present
embodiment, a component of the lubricant transferred to the
pressure roller 20 from the inside of the heating unit 9 is scraped
by the scrapers 60 (lubricant scraping member). The scrapers 60
discourage adhesion of the lubricant to the sheet P introduced into
the fixing apparatus 6.
[0083] First, a lubricant moving-around phenomenon is described. In
the above-described fixing apparatus 6, a lubricant, such as a
heat-resistant grease, is applied on the surface of each of the
heater 11 and the stay holder 12, thus reducing the friction
between the fixing belt 10 and each of the heater 11 and the stay
holder 12. The heater 11 and the stay holder 12 are urged toward
the pressure roller 20 such that the fixing belt 10 is nipped.
[0084] Accordingly, the heat-resistant grease as the lubricant
receives pressure between the fixing belt 10 and each of the heater
11 and the stay holder 12. In this state, when the fixing belt 10
is rotated by rotation of the pressure roller 20, the grease is
pressed and extended toward the ends of the heating unit 9 in the
width direction. The grease spread toward the ends may leak out
from the ends of the fixing belt 10.
[0085] The leaked grease moves around and adheres to the surface of
the fixing belt 10 by its viscosity or pressing-back from the
rotational flange 15A. The grease adhering to the surface of the
fixing belt 10 is moved to the locations of the ends of the nip
portion N constituted by the fixing belt 10 and the pressure roller
20 by, for example, being pressed by subsequently leaking grease.
When the grease moved to the locations of the ends of the nip
portion N in the width direction is nipped, pressed, and extended
by the nip portion N, the grease may be transferred to a sheet
passage area A1 in the pressure roller 20 (area that can come into
contact with the sheet P with a maximum width introducible into the
apparatus), as illustrated in FIG. 2.
[0086] If the grease having reached the area A1 in the
above-described way adheres to the sheet P at the time of image
formation, this may lead to an image defect. To avoid such a
defect, the grease can be removed before it reaches the area
A1.
[0087] As illustrated in FIG. 2, the pressure roller 20 has an area
A2 through which the sheet P does not pass (area that does not come
into contact with the sheet P with the maximum width introducible
into the apparatus) on each of the ends in its rotational axis
direction. While the grease lies in the area A2, that grease does
not stain the sheet P. Thus the scrapers 60 disposed in the area A2
can scrape the grease before it reaches the area A1. Each of the
scrapers 60 is arranged so as not to come into contact with the
area A1, through which the sheet P passes, (area that can come into
contact with the sheet P with the maximum width introducible into
the apparatus) in the pressure roller 20 and thus has a
configuration that does not substantially affect the fixing
process. The scraper 60 is described in detail below with reference
to the drawings.
[0088] The scraper 60 is a member for scraping a lubricant, such as
grease, adhering to the surface of the pressure roller 20. The
fixing apparatus 6 according to the present embodiment has a
configuration including two scrapers 60. One of the scrapers 60 is
in contact with the surface of the pressure roller 20 in the area
A2 on one end side of the pressure roller 20 in the longitudinal
direction. The other of the scrapers 60 is in contact with the
surface of the pressure roller 20 in the area A2 on another end
side of the pressure roller 20 in the longitudinal direction. If
the scraper 60 comes into contact with the surface of the pressure
roller 20 in the area A1, the surface of the pressure roller 20 may
become rough or the like, and this may affect the fixing process.
If the scraper 60 derives heat of the pressure roller 20 in the
area A1, temperature unevenness may occur in the pressure roller
20, and this may affect the fixing process. To address these
issues, the scraper 60 can be arranged so as not to be in contact
with the area A1.
[0089] The scraper 60 according to the present embodiment is spaced
from the end of the area A1 in the width direction by a small
distance in the area A2. The small distance can be on the order of
2 mm in consideration of individual differences among sheets P and
positioning errors at the time of conveyance. If the effects of the
individual differences among sheets P and the positioning errors at
the time of conveyance on the fixing process are in an allowable
range, the scraper 60 may be in contact with the whole of the area
A2.
[0090] The scraper 60 according to the present embodiment is a
rubber blade having a width of approximately 5 mm. As illustrated
in FIG. 3, one end of the scraper 60 is bonded and fixed on the
apparatus housing 30. Hereinafter, this end is referred to as fixed
edge. The other end of the scraper 60 is in contact with the
surface of the pressure roller 20. Hereinafter, this end is
referred to as contact edge. Instead of the rubber blade, a
biaxially-oriented polyethylene terephthalate (BoPET) member may
also be used as the scraper 60. The width of the scraper 60 is not
limited to approximately 5 mm and may be larger or smaller than 5
mm if it has a size sufficient for removing the grease.
[0091] The contact edge is positioned upstream of the fixed end in
the rotational direction of the pressure roller 20 (with reference
to the nip portion N). That is, the scraper 60 is in elastic
contact with the pressure roller 20 in a direction counter to the
rotational direction of the pressure roller 20. When the contact
edge is in contact with the pressure roller 20 along its surface,
the scraper 60 scrapes the grease transported together with
rotation of the pressure roller 20. The scraped grease is
accumulated in the bottom section of the apparatus housing 30 in
the fixing apparatus 6. A container or the like for collecting the
grease may be disposed in the bottom section of the apparatus
housing 30.
[0092] When the fixing apparatus 6 is in use, the above-described
scraper 60 functions as follows. That is, when the fixing belt 10
is rotated by driving of the pressure roller 20 resulting from the
execution of the fixing process, the grease gradually leaks from
the ends of the fixing belt 10 in the longitudinal direction. The
leaked grease moves along the surface of the fixing belt 10 in the
width direction of the fixing belt 10 and reaches the nip portion
N. The space between each of the ends of the fixing belt 10 and the
nip portion N is on the order of 3 mm. This space may be reduced.
For example, the end location of the fixing belt 10 and the end
location of the pressure roller 20 may coincide with each
other.
[0093] The grease is pressed by the nip portion N and transferred
from the surface of the fixing belt 10 to the surface of the
pressure roller 20. Not all of the grease adhering to the surface
of the fixing belt 10 is transferred to the surface of the pressure
roller 20 at a time. The rotation of the fixing belt 10 repeatedly
causes the surface of the pressure roller 20 and the surface of the
fixing belt 10 to come into contact with each other, and this
gradually transfers the grease to the pressure roller. In
particular, when a heating member, such as the heater 11, is near
the fixing belt 10, as in the present embodiment, the temperature
around the fixing belt 10 tends to be higher than the temperature
around the pressure roller 20. Thus when a grease in which its
viscosity reduces with an increase in temperature is used, as in
the present embodiment, because the viscosity of the grease on the
fixing belt 10 is relatively low, the grease tends to be
transferred to the pressure roller 20. Before the grease
transferred to the pressure roller 20 reaches the area A1, it is
transported to the scraper 60 by the rotation of the pressure
roller 20 and is scraped by the scraper 60.
[0094] In this way, the grease transferred to the pressure roller
20 is promptly scraped by the scraper 60. That is, because the
grease is scraped in the area A2, it does not move to the passage
area A1. Accordingly, contamination of the sheet P or an image
caused by the grease adhering to the sheet P can be suppressed.
[0095] In the foregoing description, the direction in which the
scraper 60 scrapes the grease is described as the radial direction
of the pressure roller 20. The direction in which the grease is
scraped is not limited to that direction. For example, the scraper
60 may scrape the grease by pushing it outward from the end in the
rotational axis direction of the pressure roller 20.
[0096] Specifically, the scraper 60 is arranged such that, at the
contact edge, its end near the central section in the longitudinal
direction of the pressure roller 20 is in contact with the pressure
roller 20 on the upstream side in the rotational direction of the
pressure roller 20. The scraper 60 is arranged such that its end
near the end section in the longitudinal direction of the pressure
roller 20 is in contact with the pressure roller 20 on the
downstream side in the rotational direction of the pressure roller
20. That is, the scraper 60 is in contact with the pressure roller
20 such that the longitudinal direction of the contact edge
intersects with the rotational direction of the pressure roller 20.
When the grease transported together with the rotation of the
pressure roller 20 comes into contact with the contact edge,
movement of the grease is guided from the central section toward
the end section of the pressure roller 20.
[0097] The above-described relationship applies to both of the two
scrapers 60. Thus a virtual straight line extended from the contact
edge in the longitudinal direction of one of the scrapers 60 and
that of the other of the scrapers 60 intersect with each other on
the upstream side in the rotational direction of the pressure
roller.
[0098] To scrape the grease in the above-described scraping
direction, one end of the contact edge of one of the scrapers 60
can project from one end of the pressure roller 20 in the
rotational axis direction. One end of the contact edge of the other
of the scrapers 60 can project from another end of the pressure
roller 20 in the rotational axis direction. With this
configuration, the grease can be ejected such that once the grease
have been scraped by the scraper 60, it will not adhere to the
pressure roller 20 again.
[0099] As described above, according to the present embodiment, the
scraper 60 is arranged on the pressure roller 20 in an area that
can come into contact with the fixing belt 10 and that does not
come into contact with the sheet P with the maximum width
introducible into the apparatus. Thus transferring of the grease to
the pressure roller 20 in the area that can come into contact with
the sheet P can be suppressed.
[0100] Accordingly, contamination of the sheet P or an image by a
lubricant, such as a grease, can be suppressed.
[0101] Because the scraper 60 is not in contact with the fixing
belt 10, frictional resistance to the fixing belt 10 can be
reduced. Accordingly, stability of rotation of the fixing belt 10
can be maintained.
[0102] Because the scraper 60 is not in contact with the fixing
belt 10, abrasion of the fixing belt 10 caused by frictional
sliding can be reduced. Accordingly, a reduction in the life of the
fixing belt 10 and an extension in the degree when the fixing belt
10 is damaged can be suppressed.
Second Embodiment
[0103] In the first embodiment, an example in which the scraper 60
are used as the scraping member is described. In a second
embodiment, an example in which felts 61 are used as the scraping
member is described. The configuration of the fixing apparatus 6
according to the present embodiment is substantially the same as
that in the first embodiment, except for the use of the felts 61.
Accordingly, the same reference numerals are used in the same
configuration as in the first embodiment, and the description
thereof is not repeated here. FIG. 8 is a cross-sectional
explanatory view of a fixing apparatus according to the present
embodiment taken along the line VIII-VIII in FIG. 2.
[0104] In the present embodiment, as illustrated in FIG. 8, the
felts 61 (lubricant absorbers) as the scraping member are in
contact with the surface of the pressure roller 20 in the area A2
on both ends in the rotational axis direction.
[0105] Each of the felts 61 is the scraping member using unwoven
fabric or the like for absorbing a lubricant, such as a grease,
adhering to the surface of the pressure roller 20. The fixing
apparatus 6 according to the present embodiment has a configuration
including two felts 61. One of the felts 61 is in contact with the
surface of the pressure roller 20 in the area A2 on one end side of
the pressure roller 20 in the longitudinal direction. The other of
the felts 61 is in contact with the surface of the pressure roller
20 in the area A2 on another end side of the pressure roller 20 in
the longitudinal direction.
[0106] The felt 61 has one surface bonded to the bottom section of
the apparatus housing 30 and another surface being in contact with
the surface of the pressure roller 20. The felt 61 can be a highly
flame-retardant one capable of enduring contact with the
high-temperature pressure roller 20. In the present embodiment,
aramid felt GX 0778 (trade name) of AMBIC Co., Ltd. is used as the
felt 61.
[0107] To sufficiently remove the grease, in the present
embodiment, the felt 61 having the dimensions of 5.times.8.times.3
(mm) is disposed such that it is in contact with the pressure
roller 20 in each of the conveyance direction and the width
direction by 5 mm and such that a portion of the remaining 3 mm in
the width direction protrudes from the end of the pressure roller
20. In the area where the felt 61 is in contact with the pressure
roller 20, the felt 61 is pressed in contact with the pressure
roller 20 such that its thickness is reduced from 3 mm to 2 mm.
[0108] When the fixing apparatus 6 is in use, the above-described
felt 61 functions as follows. That is, when the fixing belt 10 is
rotated by driving of the pressure roller 20 resulting from the
execution of the fixing process, the grease gradually leaks from
the ends of the fixing belt 10 in the longitudinal direction. The
leaked grease moves along the surface of the fixing belt 10 in the
width direction of the fixing belt 10 and reaches the nip portion
N. The grease is pressed by the nip portion N and transferred from
the surface of the fixing belt 10 to the surface of the pressure
roller 20. Before the grease transferred to the pressure roller 20
reaches the area A1, the grease is transported to the felt 61 by
the rotation of the pressure roller 20, and it is scraped by the
felt 61 and absorbed in the gaps in the fabric.
[0109] In this way, the grease transferred to the pressure roller
20 is promptly scraped by the felt 61. That is, because the grease
is scraped in the area A2, it does not move to the area A1.
Accordingly, contamination of the sheet P or an image caused by the
grease adhering to the sheet P can be suppressed.
[0110] The felt 61 can have an area projecting from the end of the
pressure roller 20 at a site that can come into contact with the
fixing belt 10 in the rotational axis direction of the pressure
roller 20. The felt 61 can have at least an area being in contact
with the edge section of the pressure roller 20 at a site that can
come into contact with the fixing belt 10.
[0111] In particular, when a grease having a high viscosity is
used, a part of the grease adhering to the surface of the fixing
belt 10 may be transferred in a block to the corner section (edge
section) of the end of the pressure roller 20. When the block of
the grease transferred to the edge section is rotated together with
the pressure roller 20, it gradually enters the nip portion N. With
the above-described configuration, the grease transferred from the
fixing belt 10 to the edge section of the pressure roller 20 and
having not yet reached the nip portion N can be scraped and dropped
in the block state.
[0112] Thus the amount of the grease having reached the nip portion
N can be reduced, and the amount of the grease absorbed by the felt
61 can be suppressed. This may lead to an extended period of use of
the felt 61.
[0113] As described above, according to the present embodiment, the
felt 61 is arranged on the pressure roller 20 in the area that can
come in contact with the fixing belt 10 and that does not come into
contact with the sheet P with the maximum width introducible into
the fixing apparatus 6. Thus transferring of the grease to the area
that can come into contact with the sheet P in the pressure roller
20 can be suppressed.
[0114] Accordingly, contamination of the sheet P or an image caused
by a lubricant, such as a grease, can be suppressed. Because the
felt 61 is not in contact with the fixing belt 10, the frictional
resistance to the fixing belt 10 can be reduced. Accordingly,
stability of rotation of the fixing belt 10 can be maintained.
[0115] Because the felt 61 is not in contact with the fixing belt
10, abrasion of the fixing belt 10 caused by frictional sliding can
be reduced. Accordingly, a reduction in the life of the fixing belt
10 and an extension in the degree when the fixing belt 10 is
damaged can be suppressed.
Other Embodiments
[0116] The first and second embodiments are described above. The
configurations for implementing the present invention are not
limited to the configurations described in the above
embodiments.
[0117] The fixing apparatus according to the first embodiment has a
configuration including the fixing belt and the pressure roller.
Another example configuration may be the one in which instead of
the pressure roller, a pressure belt (endless belt) is used, and
the lubricant scraping member is in contact with each of both ends
of the pressure belt in the width direction. This configuration can
also achieve substantially the same advantages.
[0118] The heating member and the pressing member in the fixing
apparatus according to the first embodiment are a ceramic heater
held by the stay holder on the inner surface of the fixing belt. As
a unit configured to heat the nip portion, a fixing belt that
generates heat by electromagnetic induction using, for example, an
excitation coil may be used. In that case, as the pressing member
for pressing the fixing belt against the pressure roller, a nip pad
or the like may be used.
[0119] The image heating apparatus described as the fixing
apparatus in each of the first and second embodiments is also
applicable as a surface heating apparatus that adjusts gloss or
surface formation of an image. The image heating apparatus can be
implemented as a single apparatus singularly settable or operable
or a component unit, other than as being embedded in an image
forming apparatus. The image forming apparatus using the image
heating apparatus is not limited to an image forming apparatus for
forming monochrome images and may be an image forming apparatus for
forming full-color images. When other devices, equipment, or
housing structures are added to the image heating apparatus
depending on the use, the image heating apparatus can be used in
various image forming apparatuses, such as printers, copiers, and
facsimile machines.
[0120] While the present invention has been described with
reference to exemplary embodiments, it is to be understood that the
invention is not limited to the disclosed exemplary embodiments.
The scope of the following claims is to be accorded the broadest
interpretation so as to encompass all such modifications and
equivalent structures and functions.
[0121] This application claims the benefit of Japanese Patent
Application No. 2013-166255, filed Aug. 9, 2013, which is hereby
incorporated by reference herein in its entirety.
* * * * *